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Biomedical subjects

A M Pearson

Publications and source records attributed to A M Pearson.

At least 19 recordsLinked to original sources
PubMed1992

Mechanism(s) involved in meat mutagen formation and inhibition.

The Maillard reaction, which involves Amadori rearrangement as a key step, also results in sugar fragmentation and free radical formation. The imidazoquinoline meat mutagens (2-amino-3-methylimidazo[4,5-f]-quinoline, or IQ, and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, or MeIQ) are formed from a reaction mixture containing alkylpyridine free radicals and creatinine. The imidazoquinoxaline meat mutagens (2-amino-3,4-dimethylimidazo[4,5-f]-quinoxaline, or MeIQx, and 2-amino-3,4,8-trimethylimidazo[4,5-f]-quinoxaline, or 4,8-DiMeIQx) may be produced by reacting a mixture containing dialkylpyrazine free radicals and creatinine. Two different pathways for free radical formation are proposed. One involves bimolecular ring formation from the enaminol form of the glycoaldehyde alkylimine and is followed by oxidative formation of the free radical. The other pathway involves formation of N,N1-dialkylpyrazinium ions from glyoxal monoalkylimine followed by reduction to produce the free radicals. The respective intermediates (glycoaldehyde alkylimine and glyoxal monoalkylamine) are formed by reacting glycoaldehyde and glyoxal with amino compounds. The glycoaldehyde system reacts faster and produces more free radicals than the glyoxal system. The reactions help to explain the formation of imidazoquinoxaline meat mutagens and their predominance in fried fish and why these mutagens are present in larger quantities in fried ground beef than the imidazoquinoline-type meat mutagens. These two pathways may not be the only mechanisms involved in formation of meat mutagens, but other free radical reactions may also contribute to meat mutagenicity and are mentioned briefly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Meat mutagens.

Explore the source record for details and available documents.

Animals↗
PubMed1990

Muscle growth and exercise.

This paper first reviews muscle growth and then considers the influence of exercise in growth. Knowledge about how muscle cells grow and some factors that may influence the growth pattern are discussed first since these effects must be considered before the influence of exercise becomes clear. Growth of muscle can occur in three ways: (1) by an increase in muscle cell numbers, (2) by an increase in muscle fiber diameter, and (3) by an increase in fiber length. All three of these mechanisms are involved in muscle growth. However, growth in cell numbers is limited to the prenatal and immediately postnatal period, with the animals and man being born with or soon reaching their full complement of muscle cells. Thus, growth occurs by either hypertrophy of the existing muscle fibers by adding additional myofibrils to increase the muscle mass or by adding new sarcomeres to the ends of the existing muscle fibers to increase their length. Both of these mechanisms occur during the growth process. Growth in the girth of the muscle fibers appears to take place by splitting of the myofibrils. This may be stimulated by development of stress creating an unequal pressure with splitting at the Z-band and development of additional SR and T-tubule systems. This adds to the diameter or girth of myofibers without any hyperplasia. The growth in length occurs at either end of the fibers and results in addition of new sarcomeres. In both cases, new myofibrillar protein must be synthesized and deposited in the muscle cells. It is suggested that adaptation by adding or removing sarcomeres is physiologically determined by the degree of force a muscle can generate that is in turn dependent on the degree of overlap of the thick and thin filaments. Thus, the amount of tension would control the number of in-series sarcomeres in a single muscle fiber. Nutrition is also known to play an important role in muscle and was discussed from the standpoint of the effects of nutritional adequacy and restriction. Although a nutritionally balanced and calorically adequate diet is required to achieve optimum muscle growth, it may be less efficient in terms of protein deposition than a moderately restricted diet. Muscle and bone deposition, however, can be limited on severely restricting the dietary intake. Although fat deposition is the first tissue to suffer on a severely restricted diet, muscle and bone follow next with the nervous system, brain and eyes being the last systems to be affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Contribution of wood smoke to in vivo formation of N-nitrosothiazolidine-4-carboxylic acid: initial studies.

The effect of administering liquid smoke or smoked food products to rats on in vivo formation of N-nitrosamino acids was investigated. Rats treated by gavage with either cysteine, formaldehyde or nitrite excreted urine containing no detectable levels of N-nitrosothiazolidine-4-carboxylic acid (NTCA). All three precursor compounds were required for NTCA formation. Two liquid smokes, when administered to rats in combination with cysteine and nitrite also produced measurable quantities of NTCA. Ascorbate inhibited in vivo formation of NTCA by approximately 90% when given to rats simultaneously with cysteine, formaldehyde, and nitrite. alpha-Tocopherol was much less effective than ascorbate in blocking NTCA formation. When smoked bacon, smoked Swiss cheese, and chicken barbecued with a sauce containing smoke flavouring were fed to rats along with nitrate, NTCA was again detected in the urine.

Acetaldehyde↗
PubMed1988

The handwriting of children with spina bifida.

As part of the Greater London Council (GLC) Spina Bifida Survey the handwriting of 131 11-year-olds with spina bifida and 56 controls was examined. The children copied the sentence "The dog sits in his box" in the course of an extensive battery of intelligence and attainment tests. Writing speed formed one scoring dimension and nine further categories were devised in collaboration with a handwriting consultant. All but one of these ten dimensions consistently discriminated between the spina bifida children and the controls, and between the spina bifida children divided according to such variables as IQ, school type, degree of disability, reading scores and presence or absence of a valve. In every case the differences were in the predicted direction, with the handwriting scores of the brighter, less damaged children, and those attending ordinary schools being higher. These findings are consistent with those obtained by other researchers and reflect an educational disadvantage in that the children with spina bifida had handwriting which was slow, with the letters being poorly formed and the words poorly spaced.

Child↗
PubMed1986

Aflatoxin carryover and clearance from tissues of laying hens.

A feeding trial was conducted to determine the levels of aflatoxins deposited in the tissues of hens fed a diet contaminated with 3310 micrograms AFB1/kg and 1680 micrograms AFB2/kg for 4 wk. At the end of aflatoxin feeding, the livers were pale, enlarged and haemorrhagic and the ovaries were significantly smaller than those from control hens and contained only small ova. Only a small fraction of the aflatoxins consumed was deposited in the tissues, either as the original compounds or as their metabolites, which were widely distributed in all tissues. The highest levels of aflatoxins were detected in the gizzard, kidneys and liver, with average total concentrations of less than 3 micrograms/kg. The lowest residue levels were detected in the breast, blood serum and leg, with breast muscle having a total concentration of less than 0.1 microgram/kg. Two days after removal of the contaminated feed, aflatoxin residues in all tissues had decreased markedly, with no aflatoxins being detected in the heart or spleen. No aflatoxin residues were detected in the breast, leg, gizzard and ovaries of hens killed 8 days after withdrawal, or in the kidneys and blood at 16 days. However, one of seven hens had measurable amounts of AFB2 in the liver 32 days after withdrawal. Although few residues were detected in most tissues after 8 days on the aflatoxin-free diet, variation existed between tissues and between individual hens in the amount of time required to achieve tissue clearance.

Aflatoxins↗
PubMed1986

Steroid hormone pathways in the pig, with special emphasis on boar odor: a review.

Although castration of male pigs grown for meat production has long been a commercial practice in order to eliminate an undesirable odor emanating from the meat upon heating, intact males (boars) grow faster, utilize feed more efficiently and produce leaner carcasses. This review outlines the biochemical pathways of steroid hormone formation in the pig, placing special emphasis on the C19-delta 16-steroids, which have been shown to produce the "urine- or perspiration-like" odor of boar meat. Analytical methods currently available for quantitation of the C19-delta 16-steroids are also reviewed, including gas chromatography-mass spectrometry, radioimmunoassays and enzyme-linked-immuno-absorbent-assays (ELISA). Finally, methods for preventing boar odor are discussed, such as environmental methods of rearing boars, genetic selection against boar odor and autoimmunization against C19-delta 16-steroids. Autoimmunization techniques appear to offer the most promise for inhibiting production of the compounds responsible for boar odor in male pigs raised for meat production, while still maintaining the advantages of improved efficiency and greater leanness.

Androgens↗
PubMed1985

Aflatoxin deposition and clearance in the eggs of laying hens.

Hens fed a diet containing 3310 micrograms of AFB1 and 1680 micrograms of AFB2 per kg feed for 28 days showed a significant decrease in egg production and egg weights by wk 3 and 4 of feeding, respectively. Transfer of aflatoxins to the eggs occurred rapidly, reaching maximum levels after 4-5 days, and remained relatively constant throughout aflatoxin feeding. The mean values for combined residue levels in eggs were less than 0.5 microgram/kg. Levels of AFB2, AFM1 and AFM2 were similar in yolk and albumen while levels of B1 and B2a were higher in the yolk. Upon removal of the aflatoxin-containing diet, residues in eggs decreased rapidly. Clearance of aflatoxin residues from the albumen occurred faster than from the yolk. Thus, no residues were detected in the albumen and in the yolk after 5 and 7 days of withdrawal, respectively. No aflatoxin residues could be recovered from whole eggs after feeding the aflatoxin-free diet for 4 days.

Aflatoxins↗
PubMed1985

Broiler aflatoxicosis with recovery after replacement of the contaminated diet.

Broiler chickens were fed a diet containing 2057 and 1323 micrograms/kg feed of aflatoxins B1 and B2, respectively, for 35 d. Effects of aflatoxins on growth, food consumption, efficiency of food utilisation and manifestations of aflatoxicosis were compared with control birds at the end of the feeding trial and at 1, 2, 4, 8 and 16 d after replacing the contaminated feed. No difference in food consumption was observed between the controls and the aflatoxin-fed chickens, but efficiency of food utilisation was decreased from 2.2 for the controls to 2.4 g food/g gain for the group fed aflatoxins. Aflatoxins caused depressed growth and enlargement of the kidney, liver, heart and gall bladder. Haemorrhagic spots were present on the surface of the muscles and some of the livers. Most livers from aflatoxin-fed birds were pale and infiltrated with lipid. After withdrawal of the food containing aflatoxins, all apparent gross lesions of aflatoxicosis disappeared, with no evidence of any lesions 8 d after removal of the contaminated diet.

Aflatoxin B1↗
PubMed1984

Tissue deposition and clearance of aflatoxins from broiler chickens fed a contaminated diet.

A study was conducted to determine aflatoxin levels in the tissues of broiler chickens that had been fed a diet containing 2057 micrograms aflatoxin B1 and 1323 micrograms aflatoxin B2/kg for 35 days. Results showed that aflatoxins were deposited in all tissues. The highest levels of aflatoxins were present in the gizzards, livers and kidneys. There was evidence that the high levels of aflatoxins B1 and B2 in the gizzards might have been caused by contamination by the gizzard contents during the slaughtering process. After feeding the aflatoxin-contaminated diet for 35 days, mean values for the combined aflatoxins were less than 3 micrograms/kg of tissue. Four days after withdrawal of the aflatoxin-contaminated ration, there were no detectable amounts of aflatoxins in any of the tissues. The results indicate that broiler chickens rapidly clear aflatoxins from their tissues once they are transferred to an aflatoxin-free diet.

Aflatoxins↗
PubMed1984

Further factors influencing N-nitrosamine formation in bacon.

The possible relationship of unsaturated fatty acids in adipose tissue to the formation of N-nitrosamines in bacon was evaluated by trials in which pigs were fed regular (control), tallow-, coconut fat- and corn oil-supplemented diets. Bacon prepared from pigs fed corn oil-supplemented diets contained significantly higher levels of N-nitrosopyrrolidine and N-nitrosodimethylamine than did control bacon samples; however, bacon produced from pigs fed a coconut fat-supplemented diet contained significantly lower levels of N-nitrosopyrrolidine. Fatty acid analyses of the adipose tissue of the bacon samples indicated that N-nitrosopyrrolidine levels in bacon correlated well with the degree of unsaturation of the adipose tissue. N-nitrosothiazolidine was detected in both brine-cured and dry-cured bacon at levels generally below 4 micrograms/kg. However, its formation was greatly reduced by the inclusion of alpha-tocopherol in the cure. The role of woodsmoke in N-nitrosothiazolidine formation in bacon is discussed.

Adipose Tissue↗
PubMed1982

Salt-its use in animal products- a human health dilemma.

High Na intake has been identified as one possible contributor to development of hypertension that occurs in 10 to 20% of the United States population. Per capita intake of salt, which is the major source of Na in the diet, is estimated to average 10 to 12 g/d. Discretionary use accounts for about 3 to 4 g, with an equal amount naturally present in unprocessed foods and 4 to 6 g being added during processing. Theories concerning the possible role of salt in development of hypertension are reviewed. As a result of the possible relationship of salt intake to hypertension, the Food and Nutrition Board has recommended that salt consumption be reduced to 3 to 8 g.capita-1.d-1. This would require a reduction in the amount of salt added by discretionary use and (or) during processing. The amount of salt found in various raw and processed animal products is presented and the role and importance of salt in these products are examined. Consideration is then given to methods that may be adopted to reduce Na consumption and the potential influence of these methods upon various animal products.

Animals↗
PubMed1981

Educational attainments of spina bifida children attending ordinary or special schools.

Children with spina bifida who attend special schools are usually found to be retarded in their school attainment compared with those who attend ordinary schools. This finding has, however, often been confounded by the fact that the special school children tend to have lower IQs. In this study two groups of children were identified from those in the Greater London Council (GLC) Spina Bifida Survey, one attending ordinary and the other special schools. There were 11 pairs of boys and 11 of girls, each pair being closely matched for IQ. Examination of their scores on attainment tests showed that while results of reading tests did not differ significantly between the two types of schools, children of both sexes at special schools were behind their ordinary school counterparts in number work. These results were supported by similar findings, using analysis of co-variance, on the larger group of children in the GLC survey. The effect of other factors such as physical handicap, presence of a valve, and time spent in hospital, were explored, and possible explanations for the findings are discussed.

Achievement↗
PubMed1981

Effects of ad libitum, maintenance and sub-maintenance feeding and of compensatory growth on some biochemical properties of muscle from weanling rabbits.

Weanling male rabbits were fed either: 1) a complete diet ad libitum (control); 2) a maintenance diet; or 3) a sub-maintenance diet. After 20 days, half of each group was slaughtered and the remainder was placed on treatment 1 until they achieved the same body weights as the controls (about 30 more days), when they were also killed. Body organs, including livers, hearts, lungs and kidneys, were significantly reduced in weight by nutritional stress. Maintenance and sub-maintenance feeding resulted in creases in ultimate muscle pH, water content and alkali-soluble and -insoluble stromal proteins. The intracellular proteins, especially the myofibrillar fraction, decreased markedly, depending on the degree of nutritional stress. Swelling of the stromal proteins was less for the underfed rabbits, indicating that nutritional stress increased the number of acid-stable corss-linkages. Calcium-induced contraction was not effected by any of the nutritional treatments. Blood enzymes were not affected by nutritional stress from the standpoint of their multiple molecular forms, mobility or band profiles. All differences in muscle characteristics disappeared during compensatory growth except for the increased amount of alkali-insoluble stroma protein. The concepts of labile, mobilizable and fixed body proteins are discussed.

Animals↗